Performance of the biased square-law sequential detector in the absence of signal.
Albert general sequential test for making R distinct decisions about distribution function
SEQUENTIAL ANALYSIS↗
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Results for “SIGNAL DETECTOR”
Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.
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Circuit detects errors in address currents for magnetic core arrays.
Address current error detector generates signal whenever error-producing conditions arise in magnetic core arrays
MEMORY STORAGE UNIT↗
System for the measurement of oscillator instability
System for measuring phase and frequency fluctuations of high precision oscillators
FREQUENCY MEASUREMENT↗
Lock detector for noise-coded signals
Circuit indicates when receiver is locked on pseudorandom-noise-coded signal. Circuit is used for reception of such digitally coded signals as scrambled voice messages or scrambled video. Circuit determines when receiver generated code is correct and synchronized with incoming signal so that receiver can track signal.
Carson, L. M.↗
Faint-object spectrograph for Space Telescope
The paper presents the Faint Object Spectrograph (FOS) for the Space Telescope to provide a digitized spectra of faint astronomical objects over the 115 to 700 nm wavelength range at resolving powers of 1000 and 100. A variety of concave gratings and prisms is employed to form nearly stigmatic spectra on one of the two Digicon photon counting detectors which are optimized for two different but overlapping ranges. The scientific goals associated with quasars, active galaxies, and objects within our solar system are discussed, and the FOS optical design features, including detectors, electronics, signal processing, power supplies, and data handling are examined. The FOS structural system, mechanism, and controls are described, along with the predicted performance capabilities in the spectral and spectropolarimetry modes. Finally, system performance parameters, including spatial resolution, time resolution, noise, and efficiency are discussed.
Harms, r. J.↗
Design Studies for a Far Infrared Absolute Spectrometer for the Cosmic Background Explorer
Unrelenting symmetry of design is required to assure the thermal balance of a cryogenically cooled, rapid scan interferometer spectrometer to be mounted in vacuum with the Cosmic Background Explorer liquid helium dewar. The instrument receives inputs from Winston cone optical flux collectors, one open to space and a second coupled to a black body reference source. A differential instrument, the spectrometer produces outputs corresponding to the Fourier transform of the spectral radiance difference between the two inputs. The two outputs are sensed by four detectors, two optimized for shorter wavelength response, and two optimized for longer wavelengths. The optical design, detector and signal channel, system sensitivity, mechanics, thermal control and cryogenics, electronics and power systems, command and control, calibration, system test requirements, and the instrument interface are discussed. Recommendations for continued work are indicated for the superconducting reflective horns, the motor bearing and drive, and design detail.
Johnson, N. J. E.↗
U.S. data processing for the IRAS project
The JPL's Scientific Data Analysis System (SDAS), which will process IRAS data and produce a catalogue of perhaps a million infrared sources in the sky, as well as other information for astronomical records, is described. The purposes of SDAS are discussed, and the major SDAS processors are shown in block diagram. The catalogue processing is addressed, mentioning the basic processing steps which will be applied to raw detector data. Signal reconstruction and conversion to astrophysical units, source detection, source confirmation, data management, and survey data products are considered in detail.
Duxbury, J. H.↗
Measurement of ultrasonic fields in transparent media using a scanning differential interferometer
An experimental system for the detection of three dimensional acoustic fields in optically transparent media using a dual beam differential interferometer is described. In this system, two coherent, parallel, focused laser beams are passed through the specimen and the interference fringe pattern which results when these beams are combined shifts linearly by an amount which is related to the optical pathlength difference between the two beams. It is shown that for small signals, the detector output is directly proportional to the amplitude of the acoustic field integrated along the optical beam path through the specimen. A water tank and motorized optical platform were constructed to allow these dual beams to be scanned through an ultrasonic field generated by a piezoelectric transducer at various distances from the transducer. Scan data for the near, Fresnel, and far zones of a uniform, circular transducer are presented and an algorithm for constructing the radial field profile from this integrated optical data, assuming cylindrical symmetry, is described.
Dockery, G. D.↗
AVIRIS onboard data handling and control
The timing and flow of detector and ancillary data for the Airborne Visible/Infrared imaging spectrometer (AVIRIS) are controlled within the instrument by its digital electronics assembly. In addition to providing detector and signal chain timing, the digital electronics receives, formats, and rate-buffers digitized science data; collects and formats ancillary (calibration and engineering) data; and merges both into a single tape record. Overall AVIRIS data handling is effected by a combination of dedicated digital electronics to control instrument timing, image data flow, and data rate buffering and a microcomputer programmed to handle real-time control of instrument mechanisms and the coordinated preparation of ancillary data.
Steinkraus, Ronald E.↗
AVIRIS onboard data handling and control
The timing and flow of detector and ancillary data for the Airborne Visible/Infrared Imaging Spectrometer (AVIRIS) are controlled within the instrument by its digital electronics assembly. In addition to providing detector and signal chain timing, the digital electronics receives, formats, and rate-buffers digitized science data; collects and formats ancillary (calibration and engineering) data; and merges both into a single tape record. Overall AVIRIS data handling is effected by a combination of dedicated digital electronics to control instrument timing, image data flow, and data rate buffering and a microcomputer programmed to handle real-time control of instrument mechanisms and the coordinated preparation of ancillary data.
Steinkraus, Ronald E.↗
Rotational fluid flow experiment: WPI/MITRE advanced space design GASCAN 2
The design and implementation is examined of an electro-mechanical system for studying vortex behavior in a microgravity environment. Most of the existing equipment was revised and redesigned as necessary. Emphasis was placed on the documentation and integration of the mechanical and electrical subsystems. Project results include the reconfiguration and thorough testing of all the hardware subsystems, the implementation of an infrared gas entrainment detector, new signal processing circuitry for the ultrasonic fluid circulation device, improved prototype interface circuits, and software for overall control of experiment design operation.
Daly, Walter F.↗
An investigation of mechanisms other than lightning to explain certain wideband plasma wave bursts detected in the Venusian nightside ionosphere
Several related topics are briefly discussed. Reviewed here is work on an investigation of plasma wave phenomena associated with the question of lightning on Venus. The work supported the contention that lightning is at least a candidate explanation for many of the 100 Hz-only Pioneer Venus orbital electric field detector (OEFD) signals. A review of the work on the investigation of mechanisms other than lightning to explain certain wideband plasma wave bursts detected in the Venusian nightside ionosphere is given. A summary is given of our analysis of data from 23 OEFD observing periods as well as a discussion of the properties of specifically multifrequency events. Our opportunity to work on this topic was not sufficient to draw any firm conclusions about the origins of the multifrequency bursts, but we call attention to what we consider to be several candidate sources. Also discussed are case studies to test for evidence of whistler mode propagation from subionospheric sources, results of a search for dispersive effects in the OEFD data, the results for a search for simultaneous 100 Hz and 730 Hz observations at altitudes below 150 km, changes with altitude in dispersive broadening effects in the time signatures of 100 Hz bursts, and a survey of activity at altitudes above 1000 km.
Carpenter, D. L.↗
Acoustical Detection Of Flameout In A Combustor
Acoustic flameout detector contains relatively simple decision circuits, because only decision it makes is whether acoustic wave in specific frequency band strong enough. If not, flameout about to occur, and acoustic flameout detector sends signal to turn off supply of fuel.
Puster, Richard L.↗
Rotational fluid flow experiment
This project which began in 1986 as part of the Worcester Polytechnic Institute (WPI) Advanced Space Design Program focuses on the design and implementation of an electromechanical system for studying vortex behavior in a microgravity environment. Most of the existing equipment was revised and redesigned by this project team, as necessary. Emphasis was placed on documentation and integration of the electrical and mechanical subsystems. Project results include reconfiguration and thorough testing of all hardware subsystems, implementation of an infrared gas entrainment detector, new signal processing circuitry for the ultrasonic fluid circulation device, improved prototype interface circuits, and software for overall control of experiment operation.
Source record↗
Experimental verification of a theoretical model of an active cladding optical fiber fluorosensor
Experiments were conducted to verify a theoretical model on the injection efficiency of sources in the cladding of an optical fiber. The theoretical results predicted an increase in the injection efficiency for higher differences in refractive indices between the core and cladding. The experimental apparatus used consisted of a glass rod 50 cm long, coated at one end with a thin film of fluorescent substance. The fluorescent substance was excited with side illumination, perpendicular to the rod axis, using a 476 nm Argon-ion laser. Part of the excited fluorescence was injected into the core and guided to a detector. The signal was measured for several different cladding refractive indices. The cladding consisted of sugar dissolved in water and the refractive index was changed by varying the sugar concentration in the solution. The results indicate that the power injected into the rod, due to evanescent wave injection, increases with the difference in refractive index which is in qualitative agreement with theory.
Albin, Sacharia↗
Ultraviolet-excimer laser-based incoherent Doppler lidar system
The topics covered include the following: principles of Doppler measurements, laser backscatter, eye safety, demonstration concepts, the wavelength-meter, the interferometer detector, return signal model, and comparison of incoherent and coherent lidars.
Mcdermid, I. Stuart↗
Micro-optics technology and sensor systems applications
The current generation of electro-optical sensors utilizing refractive and reflective optical elements require sophisticated, complex, and expensive designs. Advanced-technology-based electro-optical sensors of minimum size and weight require miniaturization of optical, electrical, and mechanical devices with an increasing trend toward integration of various components. Micro-optics technology has the potential in a number of areas to simplify optical design with improved performance. This includes internally cooled apertures, hybrid optical design, microlenses, dispersive multicolor microlenses, active dither, electronically controlled optical beam steer, and microscopic integration of micro-optics, detectors, and signal processing layers. This paper describes our approach to the development of micro-optics technology with our main emphasis for sensors applications.
Gal, George↗
Measurement of tropospheric OH by laser long-path absorption spectroscopy
OH-radicals are measured by laser long-path absorption spectroscopy. A tunable Nd:YAG/dye laser system provides broadbanded light at 308 nm. The beam is expanded to 0.3 m and pointed to an array of retroreflectors placed at a distance of 2800 m. The returning beam is separated from the outgoing beam and focused into a spectrometer of 0.3 pm resolution. A 1024 element diode array is used as a detector. The signal is digitized by a 14 bit analog to digital converter. The ultimate aim is a detection limit of 10(exp 5) molecules cm(exp -3) of OH. However the measurements in 1991 allowed only the recognition of OH absorptions corresponding to 3 x 10(exp 6) OH cm(exp -3) with a signal to noise ratio of two. Improvements of the instrument are under way. The advantages of the DOAS method are: the accuracy of detection is guaranteed because loss of OH radicals within the device is avoided, the rate of OH production by the device is negligible, and absorptions of other trace gases could be corrected for; and the calibration procedure for the device is fast and easy. The disadvantages of the system are: time resolution is about minutes because about ten spectra had to be added to keep the noise level down, the OH concentration is averaged along the whole light path, weight (500 kg) and size (4x4 m) of the device; and approximately 10 l/min of coolant and supply of 8 kW electrical power are necessary.
Kraft, Michael↗